Structural material



'No Drawing.

Patented Aug. 16, 1932 earner caries CHARLES L. NORTON, 015 BOSTON, MASSACHUSETTS STRUCTURAL MATERIAL My invention relates to structural material,particularly to building materials for exterior or interior finish; the principal ob- 'ject is the provision of interior-finish plates, slabs,or tiles combining in their structure a backing or base of stiff, porous and therefore relatively light-weight, fire-proof or at least fire resistant, material, and a hard, dense surface layer or veneer attached and intimately bonded to the backing, non-combustible, dirt-shedding, unaffected by water or ordinary household cleansing chemicals, and resistant to abrasion by scouring powders or soaps.

The preferred permeable backing mate-rlal is composed of, or comprises in large part, fibrous material, this ensures a tenacious bond between the backing and the surface layer, the latter being prepared and applied as a water-borne concrete mixture of hydraulic cement and a pulverized hard aggregate. Further, in order to produce a good cementitious bond between the backing and the surface layer, there should be incorporated in the backing material, if it does not already ccmorise it. a substance aliinitive to hydraulic cement, such as calcium or magnesium compounds, or a deposit of hydraulic cement from a dilute suspension in water; when fi:

brous material is incorporated in the backing,

it is f advantage to employ fibres which are themselves affinitive to hydraulic cement, for exampl asbestos fibres. y I

In order to produce a surface layer which shall repel dirt, be easily cleansed,and resist abrasion by scouring materials, the sub stances incorporated with hydraulic cement teform the concrete surface layer must be not on y hard. but be reduced to a powder of which the particle sizes are of the same order that of hydraulic cement, that is, little if any coarser than 100 mesh. less than 300 mesh are to be avoided, particularly if the hard aggregate'is inherently quick-setting, and therefore liable, in very 'gh dispersion, to set more quickly than is y be consistent with proper control of the process.

The term hydrauliccement,is herein used to include any cement whichwill set under Particle sizesv Application filed November 17, 1930. Serial No. 496,348.

the lime, silica and alumina mixtures coins mercially known as Portland cement.

In. order to subserve fully the uses for which the herein described structural material is intended, the surface layer must be highly polished in order to resist deposition and retention of dirt, and to be easily cleansed. Therefore, the hydraulic cement ingredient and the associated hard aggregate should be very tenaciously bonded together in a dense,

void-free structure, and, during the polishing process at least, the cement must be hardened in order to form, with the hard aggregate, a material uniformly resistant to polishing friction and abrasion.

An example of my invention, in what. I believe to be its best embodiment, is afforded by a sheet, slab, or tile of which the backing material is a compressed concrete of asbestos fibres (or the equivalent in crushed serpentine rock) and a hydraulic cement, such as is clescribed in my United States Letters Patent No. 847,293, dated March 12, 1907, and which is now generally known as asbestos wood; and of which the surface layer is a concrete comprising a hydraulic cement and pulverized, hardburned kaolin. Other hard, pulverized aggregates, such as quartz sand, or flint,will servethe purpose, but these materials do not bond as tenaciously with hydraulic cementas hard-burned kaolin, nor do they set so promptly. The intimacy of bond between cement and kaolin ensures against dis: lodgment of aggregate particles from the concrete during polishing. 4

Concrete articles comprising hydraulic cement and a hard aggregate of comminuted or pulverized quartz sand, flint, etc., will be found susceptible of receiving a high polish, but theuse of hard-burned kaolin as the sole, or predominant ingredient associated with the cement, because of the quick-setting of such concrete mixture, and also because of the unusually tenacious bond between the cement and kaolin in the final product, makes the product more amenable to polishing abrasion, which does not break the bond and remove aggregate particles as it is liable to do if other hard aggregates are employed. 7 r

The remarkable quiclcsetting property of a concrete mixture comprising hydraulic cement and hard-burned kaolin may be demonstrated as follows. Prepare for comparison mixtures of equal quantities of Portland cement and quartz sand, flint, or any other hard material (other than kaolingrog), and of equal mixtures of Portland cementand hardburned kaolin (prepared as hereinbel-ow' specified) grind each mixture, dry, in a ball mill until its particles are impalpa'bly fine and practically unsusceptible of further dimensional reduction. In each mixture the cement andhard aggregatewill be mutually andevenly distributed, so that every particle of'each ingredient will have-the same propinquity to particles of the other. Then make a water mixture of each pulverized solid mixture, using the quantity theoretically required for the setting of the cement therein, and cast each in a shallow tray, to equal depths. --By the needle test, it will be determined that the cement-kaolin mixture starts its initial setin abouttwo minutes, and is complete in ten minutes, whereas in the other mixture, initial set is detected in from two to two and a half hours and completed in about five hours. If the hard-burned. kaolin and cement be reduced tothe utmostextremity of fineness by grinding, -it willtalre itsinitial set in a few seconds.

lf porousor permeable materials be-used for the back? ngwhich do not ordinarily containsubstances aifin'iti-ve to hydraulic cement, they should be impregnated, at? the --'side;to which the surface layer is to be applied, with a deposit of such a sul'istance,- for instance calcium or magnesium hydraulic cements. For example, a stiff permeable board of'veg'etable'fibres, supplied with a deposit of---hydroxid or oxychlorid of magnesium, will bond-much more securely with a hydraulic cement concrete applied to its surface, than without such impregnation.

An example of my invention, comprising a backing orbase layer of asbestos wood and the hard aggregate concrete surface layer bonded thereto may be made in either of two .waysz-By applying the surface layer concrete-materialtoa preformed sheet of ashestos wood, or by overlaying the-wet-asbestos woodmixture with a surface of water-borne surfacelayerconcrete mixture in a filter press and then proceeding in the manner-described in my said patent. Though the former method is slower andmore difficult than the latter; in essentials the two are alike the controlling conditions may be better understood from a description of the slower method, which is as follows r The sheetofasbestos wood whiohjis to constitute the base of-the final product is prepared by soaking in water to full saturation ratnn' as a precaution against local inhalation of air by theconcrete material in -the initial setting stage. I have observed that if the conditions of manufacture involve access of air to-the under side of the cast shape during the process, the concrete material draws air into; itself locally, producing bubbles 'or vo-ids in 1159 00613 tliat-such bubbles occasionally. burst through the upper exposed surface, forming craters, and that these voids are of va'rious and sometimes consid arable size. Their presence is obviously detri mental and should be guarded against. Retention of saturation by water in a permeable base, or "the employment of an impermeable base on which to make the cast, has been accompanied by non-production of bubbles or :voids in the 'concrete'body. 1

Prepare a water-borne concrete mixture, rich in cement, preferably of equalweightproportions of'Portland cement and a kaolin grog made by burningkaolin at a temperature approximating-to 3000 F., then pulverizing to a fineness that will all pass-a mesh screen. This kind of mate ial and its manufacture, is described in UnitedStates Patent No. 1,530,620, dated March 17, 1925, grantedto Harter and Kchler; The'water proportion need not be closely limited, a fairly; free flowing creamy composition is suit able.

The-fine par'ticles, both of'cement and kaolim will carry into the water mixture a considerable quantity. of adsorbed air, which must'be' eliminated otherwise occluded voids will form inthe concrete, some of'quite considerable size} The airma'ybeeffectirelyremoved by subjecting the water mixture to vacuum-exhaust until it ceases to froth.

The surface layer'mixture having been jthus'prepared, flow it over the wet asbestos wood sheet, covering all the surface; tilt the sheet from side to side slightly, and jar it as by tapping the'under side sharply, so as to even and level the surface coating.

By reason of the water saturation of the base sheet, excess water is now eliminated from the surface coating by outward evaporation only, and thefluid surface mixture unites with the base sheet, fOImlIlgllltlIfifllW ly an intimate bond-between the base-and the-surface layer, to which bonding the fithe approach of initial set. /Vhen the con-' crete mixture has thus ceased to be free-flowing and, being damp and not yet set, is ca pable of internal flow under pressure, the elimination of water therefrom should be accelerated, and pressure should be applied at'or about the same time, in order to compact the damp mixture and eliminate substantially all the voids therein. This may be done by applying adry bibuloussheet, such as blotting paper, to the surface ofthe coatinglayer, and subjecting the layer to roller pressure through the paper. pressure, in the method being described, need 1 be no heavier than can be applied by a handoperated roller. Or, a roller "aclietedw th bibulous material may be applied directly to the damp coating. Or, pressuremay be applied by means of a'filter-sheet, as of cloth, stretched in a frame, and'expressed water re moved as it comes through the sheet. Roller pressure on the cloth is recommended, the roller may be of bibulous material, or be followed by any water-removin appliance. If

a pervious filter'pad, stiff enough to exert pressure on the surface of the concrete layer, be used to compress and compact it, and at the same time exhaust be applied to the upper surface of the pad, the eifect of combined pressure and elimination of the last excess water will be satisfactorilyproduced.

Presently the coating will take its initial set. Thereafter the composite sheet is allowed to remain for six or seven days in a moist atmosphere, to give the concrete surface layer its final set.

When finally set, the concrete surface layer presents a dully reflecting surface which, to render the structural material constituted by the compositesheet suitable in all respects er, and formation of the asbestos wood base,

and which is preferable forobvi'ous economical reasons, involves the preparation of the asbestos wood fibre concrete mixture, which is first spread on the filter bed of a hydraulic press, inthe manner described in-my said patent.

The surface-layer concrete mixture is prepared as for the open-evaporation meth 0d above described, except that it is notnecessary to submit it to a preliminary exhaustion of occluded air, because the elimination of. water by the press-method carries the air out of the mixture and into the base layer or sheet, and thence in large measure at least,

out through thefilter bed. While the surface layer mixture must be wet enough to flow internally under pressure, it will not be found necessary to use so large a water proportion as in the open evaporation method.

When the two wet mixtures have been thus placed inthe press, the pr ss head (which should be slightly oiled to prevent the surface layer mixture from sticking to it) isbrought down. If the asbestos wood mixture has been fairly evenly spread-in the press, minor irregularities in its surface will do no harm; lateral andinternal flow distributes the two layers and produces ultimate tenacious bonding between the two. -After a short time (usually not more than thirty seconds) initial setting of the surface layer will have taken place, the press may be opened, and the composite sheet removed, to be placed, with others later superposed with steel sheets between them," in a final setting press, there to remain for six or seven days for final setting.

Hardening and polishing then follows, as with the material made by the open evaporation process. v

If a very thin surface layer is to be applied to the asbestos wood base, the asbestos wood mixture is first placed alone in the press, the

head brought down and the mixture pressec to an even fiat surface by pressure which much less than that required for the completion of an asbestos wood sheet, and which leaves a fairly large proportion of excess water in the mixture. The press is then opened, and a charge of surface-layer mixture placed on the flattened asbestos wood material. By varying the volume of this surface-layer mixture and also by varyingits water content, the thickness of the finally completed surface layer can be adjusted as desired. The operation of the press and subsequent treatment of the composite sheets, will be as above described. Surface coatings of the fine hard concrete as thin as one one hundredth of an inch have been thus applied to an asbestos wood sheet-base.

While the liability of composite sheets of asbestos wood and concrete veneer, made as above described, to warp is quite small, this contingency may beprovided for by applying to the unveneered side. of the sheet a concrete coating of composition similar to that of the first coating. If all the conditions req -uisite tovthe formation; of aco-mpletely :fin .ished, compacted, flllCl-POlIShBd'COHCIBtB surface l-ayer;hereinabove setforth, be observed,

til

the'composite, double surfaced sheet will be available in situationswwhen,both' sides are .-:to be in EYIQW- --If the second ssurface layer be only for "purposesqof:prevention of warping-,the precautions directedtoiprevention of abubble-voids, and-the finalpolishing,1maybe neglected Compression during initial set- ;--t1;ng 1s, however, toberecommended. Such atback-layermayrbefapplied'either by the open evaporation, orthe closed press method.

- The structural material; madeby either-of I the foregoing methods, is quitegeasily worked with tools, may be sawn and trimmed,i or bored to -rece1ve,fasten1ngs. The natural color of the surface concrete is pleasing; other colors'may beproduced by'mixing pigments with the cement and hard aggregate concrete RHIXtHIBS"Ofi-COIllZIZtSlllIlg colors may be employed tombtain colorxpattern. effects, either regular or irregular. The hard, polished SUI-.1 *face ofithencoating materlal well adapts it to* interion :fiIHSh j and decorative purposes.

In cross section, the composite: material wstructure grades- -from the porous base, through a Very narrow zone whereinthe base and surface materlalabondi together, to the dense, compact, and hardsurface coating Iwhichterminateswith its.- polishednnd re-v fractory:hard-surface. iThecharacter of the base material adapts the composite sheet to v all modes of;application to wall, ceiling or floor surfaces, including cementitious attach- I mentor embedment; qThe character of the surface which will be exposed, is as above de-- scribedgand renders the; materialeXcellent' for all structural finish purposes. 5

: In-recapitulation, it may be observed, that the watery composition ofsurface-layer con-' crete mixture comprises alarge PPOPOIlZlOIl of hydrauliccement, and an associated hard aggregate-which is of the same orderof-particle 15 size as thecement; so that-practically every particle 1 of either component will bebonded .-to particles-of the other, and the whole sur- --.face, will be adaptedto uniform polishing;

"-zthat the waterz proportion isfsuch as to -ensure progressive uniform mutualassociation of-the solidcomponents, and to-permit sufficient;-internal flow under-pressure to-.con-

I denseithe concrete and eliminate voids therefrom;;that adsorbed or occluded air is: elimi- .-.nated before tthemixture sets initially; that entrance oflair isprevented; and that, for the-- usually. indlspensable polish ngprocess,

the cement ingredient is-har-dened during, and'preferablyalso --before,.the polishing opso...

erati on.

. Also; that-the base-to-which the fine concrete surface layeris'applied ispermeable,

preferably fibrous,. contains asubstance af-.

finitiveto hydraulic cement,-= and istherefore bothw physically and chemically; adapted to base.

of the same order'as that of the associated cement, bonded by said cement to said base.

2. In structural material,- the combination of a permeable; base comprising substance aflinitive to hydrauliccement, and a surfacfi layer comprising hydraulic -cement and hard-burned k'aolin-comminuted to aparticle size of the same orderas that of the associated cement, bondedbysaid cementtoisaid 3'. In structural material, the-combination of a permeable base, comprising substanceaffinitive to hydraulic cement, and asurf-ace layer comprising a highrproportion-of hydraulic cement and hard-burned kaolin com' minuted to particle'sizeof the same: order as that of theassociated; cement, bonded by; said cement to saidabase, I r

I 4. In structural materiah the combination aflinitive to hydraulic cement,-and a voidfree surface layer comprisinga'highwproportion of hydrauliccemenhand hard burned kaolin comminuted to-- particle size "of the of a permeable base: comprisingsubstanc d same order as thatoftheassociatedcement,

bonded-by said'cement to saidibase.

5'. In structural material,--the combination of a permeable base 1 comprising substance affinitivetohydraulio cement,--and a surface layer comprising; hydraulic cement-and hard-burned kaolin commin'utedpto particle size of the same order as: that' of the-associated cement, bonded by said'cementto said "base, the cementof'saidlayer hardened, angl thelayer highly. polished;

6. In structural material, the combination of a permeable base comprising fibrous material and a substance afinitive to hydraulic cement, and a surface layer comprising 113%;

.draulic Cement and a hard aggregate com- .minuted to particle size of'thesame order as that of the associated cement, bonded by-said cement to. said base.

7. In structural material, the combination 1 of apermeable base comprisingfibrousma'terial and a. substance affinitive to hydraulic cement and a surface layer .comprisinghydraulic cement. and. hard burned :kaolin: comminuted .to ,particle size, of. thesame ordei f 13 as that of the associated cement, bonded by said cement to said base.

8. In structural material, the combination of a permeable base comprising fibrous material and a substance affinitive to hydraulic cement, and a surface layer comprising a high proportion of hydraulic cement and hard-burned kaolin comminuted to particle size of the same order as that of the associated cement,bonded by said cement to said base.

9. I11 structural material, the combination of a permeable base comprising fibrous ma terial and a substance afiinitive to hydraulic cement, and a void-free surface layer comprising hydraulic cement and hard-burned kaolin comminuted to particle size of the 7 same order as that of the associated cement,

bonded by said cement to said base.

10. In structural material, the combination of a permeable base comprising fibrous material and a substance afiinitive to hydraulic cement, and a void-free surface layer comprising a high proportion of hydraulic cetion of a permeable base of concreted asbestos fibres with a hydrauliccement, and a voidfree surface layer comprising a high proportic-n of hydraulic cement and hard-burned kaolin comminuted to particle size of the same order as that of the associated cement, bonded by said cement to said base, the cement of said layer hardened, and the layer highly polished.

Signed by me at Cambridge, Massachusetts this 13th day of November 1930.

CHARLES L. NORTON.

ment and hard-burned kaolin comminuted to particle size of the same order as that of the terial and a substance aflinitive to hydraulic cement, and a void-free surface layer comprising hydraulic cement and hard-burned kaolin comminuted to particle size of the same order as that of the associated cement, bonded by said cement to said base, the cement of said layer hardened, and the layer highly polished.

13. In structural material, the combination of a permeable base comprising fibrous material and a substance aifinitive to hydraulic cement, and a void-free surface layer comprising a high proportion of hydraulic cement and hard-burned kaolin comminuted to particle size of the same order as that of the associated cement, bonded by said cement to said base, the cement of said layer hardened, and the layer highly polished.

14. In structural material, the combination of a permeable base of concreted asbestos fibres with a hydraulic cement, and a surface layer comprising hydraulic cement and hardburned kaolin comminuted to particle size of the same order as that of the associated cement, bonded by said cement to said base. 

